The present invention relates generally to moisture analyzers. More specifically, the present invention relates to a continuous flow moisture analyzer for determining the moisture content in a liquid sample material under test.
Various manufacturing processes, chemical reactions, and laws attendant certain industries require that the percentage of certain volatile fluids of interest present within a product be known. Indeed, the determination of moisture (or volatile) content in materials is of such importance in so many fields that a variety of devices and analytical methods have been developed to provide such information.
Moisture analysis devices include, for example, vacuum ovens and convection ovens which heat a test sample of the product to a temperature commensurate with the volatile fluid of interest to cause evaporation of such fluid. Devices of this type are often referred to as loss on drying analyzers. Using a loss on drying moisture analyzer, the resulting reduction in weight of the test sample provides data for computing the percent by weight of the volatile fluid of interest in the test sample. Various computational techniques may be employed to forecast the percentage determination based upon the initial weight loss rate. Such computational approximations reduce the time required to complete a test without serious derogation of the accuracy of the determination. Loss on drying techniques are limited to approximately 0.1% minimum moisture loss due to secondary effects such as convective air currents, buoyancy effects, and temperature gradients. In addition, loss on drying techniques can incur some degree of measurement error relative to the accuracy of the scale used for weighing the test sample.
Other moisture analysis devices employ sensors that measure the quantity of volatile fluid in a gas stream to determine the amount of volatile fluid in a test sample. For example, one such moisture analyzer includes a test sample heater, a dry carrier gas flow system, and a moisture transducer. The moisture analyzer heats a sample of test material contained in a septum bottle. The dry gas is injected into the septum bottle and absorbs the moisture out of the sample material. The dry gas, carrying the moisture from the sample, is ejected from the septum bottle and transported to the moisture transducer where the moisture content of the flowing gas is measured. A processor then integrates the varying moisture signal and converts the integrated signal to total moisture content. Using the sample weight and the total moisture content value, the moisture concentration in the test sample is subsequently calculated.
Unfortunately, problems with moisture analysis devices such as pre-existing moisture levels, transient response times, and contamination can render the measurement of moisture content inaccurate. In one moisture analyzer, uncontrolled moisture can be introduced into the dry carrier gas flow system. This uncontrolled moisture results in a non-consistent baseline, which consequently leads to inaccuracy in the measurement of the moisture content in the sample material.
In some manufacturing environments, the test sample under consideration is a liquid sample material such as petroleum products, oils, liquid silicon, liquid chemicals, liquid food products, and so forth. Additional problems exist with the use of moisture analysis devices to determine the moisture content in these liquid sample materials. The moisture may be water contamination or another liquid contaminant in the liquid sample material. For example, in test situations in which water is the volatile fluid of interest present within the liquid sample material, loss on drying techniques may be rendered inaccurate because such techniques eliminate all volatile liquids rather than just the water. In addition, when a liquid sample material is placed in the septum bottle discussed above, the ratio of the surface area to volume of the liquid sample material may be insufficient for enabling the dry gas to efficiently absorb the water from the liquid sample material.
An analytical moisture analysis method known as the Karl Fischer moisture analysis technique is a method of titrating a test sample with a reagent to determine trace amounts of water in the test sample. Karl Fischer titration employs a specific reaction to consume water, independent of the presence of other volatile substances, and can be used to determine the moisture content in liquid sample materials. Unfortunately, chemical analysis methods, such as Karl Fischer titration, rely on the use of various reagents which may be toxic. Moreover, such chemical analysis methods usually require very skilled operators and are often quite time consuming.
Accordingly, it is an advantage of the present invention that a continuous flow moisture analyzer is provided.
It is another advantage of the present invention the continuous flow moisture analyzer efficiently and accurately determines the moisture content in a liquid sample material.
It is another advantage of the present invention that the continuous flow moisture analyzer enables moisture to be effectively evolved from a liquid sample material.
It is yet another advantage of the present invention that the continuous flow moisture analyzer accurately determines the moisture content in a liquid sample material by substantially preventing the introduction of uncontrolled moisture in a gas flow system of the moisture analyzer.
The above and other advantages of the present invention are carried out in one form by a continuous flow moisture analyzer for determining moisture content in a liquid sample material. The moisture analyzer includes an injection system for delivering the liquid sample material, the injection system including an injector tube. An evaporator has a first end for receiving the injector tube and a second end. The injector tube provides the liquid sample material to the evaporator at the first end. A carrier gas inlet in fluid communication with the second end of the evaporator provides a carrier gas to the evaporator at the second end. The carrier gas absorbs moisture from the liquid sample material in the evaporator. A moisture sensor in fluid communication with the evaporator detects the moisture in the carrier gas.